This invention relates to medical imaging in general, and specifically to a system and method for the detection and localization in situ of hypermetabolic tissue, particularly malignant tissue, during medical procedures such as diagnostic endoscopy and oncological surgery.
Endoscopy entails the examination of an internal organ of the human body by insertion into the organ of two flexible fiber optic bundles contained within an outer flexible sheath. One fiber optic bundle illuminates the organ tissue and the second bundle conveys the image of the illuminated tissue back to the eye of the diagnostician or to a video camera. Historically, during endoscopic procedures the diagnostician, such as a gastroenterologist, has determined which areas of tissue are normal and which, if any, areas are abnormal and require biopsy solely by visual inspection of the endoscopic field of view.
Similarly, during surgical procedures the surgeon generally has determined which areas of tissue are normal and which areas are abnormal and therefore require resection (removal) primarily by visual examination of the tissue in the surgical field of view.
Differentiation of tissue solely by the criterion of visual appearance has several significant disadvantages. During an endoscopic procedure, for example, an area of malignant tissue may be too small to be observed even during careful visual inspection through the endoscope. The published literature in the field of gastroenterological endoscopy, for example, contains numerous references to cases in which an initial endoscopic examination failed to reveal the presence of malignant tissue, while subsequent examination after a period of a few months revealed detectable malignancy. The prevalence of this clinical phenomenon suggests that there is a minimum size threshold for visual detection of an area of malignancy, and that a technique which lowered the visual detection threshold would allow earlier detection of malignancy than is currently possible. In addition, current clinical practice is to biopsy all areas of tissue whose appearance is "borderline", i.e. neither definitely normal or abnormal. A method which would allow the unequivocal differentiation of normal from malignant tissue in situ would thus eliminate the need for numerous biopsies currently being performed.
Similarly, during oncological (tumor) surgery, differences between normal and malignant tissue are often not visually apparent in the surgical field of view, and tumors frequently do not have distinct boundaries. In addition, infiltration of tumor margins by malignant tissue is not visible to the unaided eye. Thus, a method which enhanced the oncological surgeon's ability to distinguish between normal and malignant tissue during the surgical procedure would allow more accurate and thorough resection of malignant tissue.
The need for more accurate detection and localization of malignant tissue in both endoscopy and surgery has led to the development of several techniques to supplement visual inspection.
For endoscopic applications, several attempts have been made to enhance the visual detection of malignant tissue using dyes which theoretically are absorbed at a higher rate by malignant tissue than by adjacent normal tissue. In practice, the disadvantage of this approach has been that the specificity of absorption of the dyes by malignant tissue is not sufficient to render the technique useful as a routine diagnostic tool.
For oncological surgery applications, a handheld probe has been developed which detects photon emission from tissue which has been treated preoperatively with radioactive tumor-specific antibody. The probe is manually swept over the general area of the tumor and those areas of high photon emission are assumed to be tumor tissue and are resected. The disadvantages of this approach are the time-consuming and laborious nature of the manual scanning procedure and the inability of the device to generate a coherent two-dimensional image of the surgical field of view.
It is thus obvious that the present state of the endoscopic and surgical arts do not offer a sufficiently practical and accurate method for endoscopic and surgical localization of malignant tissue in situ. An ideal system for endoscopic and surgical localization would combine a significant reduction in the size threshold for detection of very small, newly developing areas of malignant tissue, intrinsic visual registration of the image of the abnormal tissue on the image of the endoscopic or surgical field of view, ease of use in the diagnostic suite or the operating room, and rapid image acquisition, analysis, enhancement and display. Such a system would satisfy an important need in current diagnostic and surgical practice. It is the object of the present invention to provide a system and method fulfilling this need.